The invention relates to a feller head for a tree felling apparatus.
Feller heads connected to articulated booms of self-powered vehicles are well known and commonly used in mechanized forestry operations. For example, such feller heads are disclosed in U.S. Pat. No. 3,749,143 to Hamilton or U.S. Pat. No. 3,796,242 to Albright. However, there have been limitations placed on the use of such boom-mounted feller heads. For example, they have been limited in the size of tree which can be cut. If the feller heads are simply scaled larger for larger diameter trees, the size and weight make boom-mounting impractical.
As a consequence, previous feller heads adapted for larger diameter trees are not suitable for boom-mounting, but are mounted directly on the front of the vehicle as seen, for example, in U.S. Pat. Nos. 3,874,432 and 3,946,775, both to Albright.
Such feller heads mounted on the front of a tractor must approach the tree trunk very closely. The terrain or obstacles adjacent the tree may make this impractical. U.S. Pat. No. 3,946,775 discloses a stump gripper below the chain saw of a feller head so the feller head is secured to the portion of the tree trunk remaining in the ground.
One reason why prior art feller heads for larger diameter trees have been too large for boom-mounting has been the size of head required to accommodate the degree of movement of the chain saw required to sever larger trees. Generally speaking, two different types of chain saw movement have been suggested. For example, chain saws pivotable about a point in the feller head are found in U.S. Pat. Nos. 2,882,941; 3,885,610; 3,976,111; 3,991,799; 3,074,447; and 3,726,326. This last patent, U.S. Pat. No. 3,726,326 to Coleman, discloses a tree-felling machine with a second chain saw which moves in a different manner while cutting the tree. This saw is mounted on a carriage which moves from end to end on an elongate horizontal plate. In either case, the size of head required to accommodate the movement for severing larger trees is too large for boom-mounting.
U.S. Pat. No. 2,882,941 to Pope discloses a saw which moves through a relatively small angle in cutting trees. However, this is achieved by mounting the saw on a control arm for rotation about a bearing. The use of the relatively long control arm is undesirable with the design of a compact feller head.
U.S. Pat. No. 2,846,175 to Sexton discloses a support for a tree-topping apparatus where the frame of a saw is provided with a projection at its bottom that fits into arcuate slots.